diff --git a/gitnexus/src/server/git-clone.ts b/gitnexus/src/server/git-clone.ts
index 0f7bc2653..53b0ea2e6 100644
--- a/gitnexus/src/server/git-clone.ts
+++ b/gitnexus/src/server/git-clone.ts
@@ -139,6 +139,23 @@ function assertNotPrivateIPv6(ip: string): void {
   if (lower.includes(':ffff:')) {
     throw new Error('Cloning from private/internal addresses is not allowed');
   }
+
+  // IPv4-compatible IPv6 (RFC 4291 § 2.5.5.1, deprecated form: ::w.x.y.z).
+  // Node's URL parser collapses http://[::127.0.0.1]/ to "::7f00:1" — the IPv4
+  // is hidden in the last 32 bits without the ::ffff: marker, so the check
+  // above misses it. The form is still routable to the embedded IPv4 on most
+  // network stacks, so any address compressed to ::xxxx[:yyyy] must be blocked.
+  if (/^::[0-9a-f]{1,4}(:[0-9a-f]{1,4})?$/.test(lower)) {
+    throw new Error('Cloning from private/internal addresses is not allowed');
+  }
+
+  // NAT64 well-known prefix (RFC 6052 § 2.1: 64:ff9b::/96, plus the local
+  // 64:ff9b:1::/48 from RFC 8215). Maps any IPv4 address — including private
+  // ranges — into IPv6, so a host with NAT64 can reach the embedded IPv4 via
+  // e.g. 64:ff9b::7f00:1 → 127.0.0.1.
+  if (lower.startsWith('64:ff9b:')) {
+    throw new Error('Cloning from private/internal addresses is not allowed');
+  }
 }
 
 function assertNotPrivateIPv4(ip: string): void {
diff --git a/gitnexus/test/unit/git-clone.test.ts b/gitnexus/test/unit/git-clone.test.ts
index 832f95641..6364cd372 100644
--- a/gitnexus/test/unit/git-clone.test.ts
+++ b/gitnexus/test/unit/git-clone.test.ts
@@ -96,6 +96,25 @@ describe('git-clone', () => {
       );
     });
 
+    it('blocks IPv4-compatible IPv6 (RFC 4291 deprecated, ::w.x.y.z)', () => {
+      // Node's URL parser collapses ::127.0.0.1 to ::7f00:1 — no ::ffff: marker,
+      // but still routable to 127.0.0.1 on most stacks.
+      expect(() => validateGitUrl('http://[::127.0.0.1]/repo.git')).toThrow('private/internal');
+      expect(() => validateGitUrl('http://[::7f00:1]/repo.git')).toThrow('private/internal');
+      // 169.254.169.254 (cloud metadata) embedded as IPv4-compatible
+      expect(() => validateGitUrl('http://[::a9fe:a9fe]/repo.git')).toThrow('private/internal');
+    });
+
+    it('blocks NAT64 well-known prefix (64:ff9b::/96)', () => {
+      // 64:ff9b::7f00:1 → 127.0.0.1 via NAT64 translation
+      expect(() => validateGitUrl('http://[64:ff9b::7f00:1]/repo.git')).toThrow('private/internal');
+      expect(() => validateGitUrl('http://[64:ff9b::a9fe:a9fe]/repo.git')).toThrow(
+        'private/internal',
+      );
+      // RFC 8215 local NAT64 prefix
+      expect(() => validateGitUrl('http://[64:ff9b:1::1]/repo.git')).toThrow('private/internal');
+    });
+
     it('does not block valid public IPs', () => {
       expect(() => validateGitUrl('https://140.82.121.4/repo.git')).not.toThrow();
     });